# CVE-2026-65927 — Apache Tomcat

> As of 2026-08-26, CVE-2026-65927 is a HIGH-severity vulnerability in Apache Tomcat, CVSS v3.1 7.5, EPSS 0.5% (41.5th percentile). Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2026-65927, most recently “Apache Tomcat 11.0.25 Fixes 11 Vulnerabilities Including HTTP/2 DoS, Authorization Bypass, and Auth Fail-Open Flaws — NVD Scores 5 of 11 CRITICAL/HIGH Despite Apache's Low/Moderate Ratings”.

**Last updated:** 2026-08-26

## What is CVE-2026-65927?

Off-by-one Error vulnerability in Apache Tomcat impacting the [N] flag on the rewrite valves causes rewrite processing to restart at the second rule rather than the first rule. This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.24, from 10.1.0-M1 through 10.1.57, from 9.0.0.M1 through 9.0.120. The following versions were EOL at the time the CVE was created but are known to be affected: from 8.5.0 through 8.5.100. Other unsupported versions may also be affected. Users are recommended to upgrade to version 11.0.25, 10.1.58 or 9.0.121 which fix the issue.

The record classifies CVE-2026-65927 under weakness class [CWE-193](https://cwe.mitre.org/data/definitions/193.html). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 19 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 7.5 — HIGH (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **EPSS (FIRST):** 0.5% probability of exploitation in the next 30 days, higher than 41.5% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 5.4/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-08-25, last modified 2026-08-26

## Is CVE-2026-65927 being exploited?

No public exploitation evidence for CVE-2026-65927 is recorded in the sources Threadlinqs tracks — CISA KEV, Exploit-DB, public proof-of-concept repositories and ProjectDiscovery Nuclei — as of 2026-08-26. That is an absence of evidence in those feeds, not a guarantee that the vulnerability is unexploited.

## Affected products and versions

- **Apache Software Foundation**: Apache Tomcat

## How to fix CVE-2026-65927

Vendor advisory: [https://lists.apache.org/thread/st1dx1zyn5y7ny2s0sscmh6lrv3worr4](https://lists.apache.org/thread/st1dx1zyn5y7ny2s0sscmh6lrv3worr4). Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory.

## Threat activity tracking CVE-2026-65927

1 tracked threat in the Threadlinqs corpus references CVE-2026-65927, either in the campaign’s CVE list or as an indicator on the campaign record.

- [Apache Tomcat 11.0.25 Fixes 11 Vulnerabilities Including HTTP/2 DoS, Authorization Bypass, and Auth Fail-Open Flaws — NVD Scores 5 of 11 CRITICAL/HIGH Despite Apache's Low/Moderate Ratings](https://intel.threadlinqs.com/threat/TL-2026-2159) — CRITICAL · 2026-08-26

## Sources

Enriched from CVE.org, NVD, FIRST EPSS, GitHub Security Advisories. Last verified by Threadlinqs on 2026-08-27. This product uses the NVD API but is not endorsed or certified by the NVD.

**Vendor advisory and patch**

- [lists.apache.org — vendor advisory](https://lists.apache.org/thread/st1dx1zyn5y7ny2s0sscmh6lrv3worr4)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-65927
Full detection coverage and IOCs for threats exploiting CVE-2026-65927 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp